1. Field of the Invention
This invention relates to a webbing retractor used in a seatbelt system for protecting an occupant in an emergency situation of a vehicle, for winding a webbing for restraining the occupant.
2. Description of the Prior Art
A webbing retractor used in a seatbelt system is adapted to wind an end portion of a webbing for restraining an occupant by its biasing force and to instantaneously stop the unwinding of the webbing by its locking device in an emergency situation of a vehicle.
This locking device, being required to reliably support an inertial force of the occupant to be violently moved in a direction of collision in an emergency situation of a vehicle, must have a mechanical strength of a high value. From this reason, heretofore, there has been widely used such locking means in which a ratchet wheel is solidly secured to a takeup shaft, and a lock bar journalled on a frame is meshed with this ratchet wheel.
The meshing means of the lock bar and the ratchet wheel solidly secured to this takeup shaft makes it possible to reliably lock the takeup shaft, however, presents a disadvantage of increasing the outer diameter of the webbing retractor.
Additionally, in a locking mechanism not using the combination of the lock bar and the ratchet wheel solidly secured to the takeup shaft, an unbalanced rotation may be generated with the lock member rotating along with the takeup shaft and loosenesses may occur between the lock member and the takeup shaft, thereby causing an instable acceleration of response.